Puppy Linux is an evolutionary operating system, based on GNU Linux. What's different here is that Puppy is extraordinarily small, yet quite full featured. Puppy Linux can boot into a 64MB ramdisk, and that's it, the whole caboodle runs in RAM.

Unlike live CD distributions that have to keep pulling stuff off the CD, Puppy in its entirety loads into RAM. This means that all applications start in the blink of an eye and respond to user input instantly.

Puppy occupies about 50-60M on my USB Flash drive, CDROM, or whatever is the storage media.

When Puppy boots, everything uncompresses into a RAM area that we call a "ramdisk". The live-CD will bootup on systems with only 32M RAM, but the more RAM you have the more Puppy is able to keep files permanently in ramdisk hence more speed. A PC with 128M RAM is the recommended minimum.

Note that Puppy will automatically use a swap partition if it exists. When booting from a USB Flash device, Puppy tries to load all the Flash files into physical RAM, but if there is not enough RAM then Puppy is able to copy the excess to a swap partition if it exists. This eliminates writes to the Flash memory during a session, greatly extending its life span.

You may need to have a swap partition to run Firefox or Mozilla on PCs with less than 64M RAM. Certainly, for a PC with only 32M RAM, a swap partition is necessary to run most of the large GUI applications.